Former police sergeant Dias has admitted that he contacted the paper to “blow the whistle” about the internal report after reading a “misleading press statement denying racism in Cleveland Police”.

He has denied leaking any documents to the paper but insists he told police about the call to the Echo.

He told Press Gazette: “I felt there was no options other than make public my genuine concerns regarding ‘institutional racism’ within Cleveland Police.

“The personal and professional impact, for doing what I believed was the right thing to do, has been devastating.

“The investigation and extensive use of surveillance is a disgrace.”

Dias said he discovered that he, his colleague and the journalists had been targeted via documents he acquired through the Subject Access Request clause under the Data Protection Act.

According to Dias and Matthews, the national journalist said to have been targeted for surveillance had previously written articles that exposed misconduct at Cleveland Police.

Cleveland Police’s surveillance requests were made under the Regulation of Investigatory Powers Act, which allowed police forces to sign off their own applications to view journalists’ call records.

This law was amended in March 2015 after the Press Gazette Save Our Sources campaign to require that police requests to view journalists’ call records in order to identity a confidential source needed approval from a judge.

Cleveland Police told Press Gazette it could “neither confirm nor deny” whether it had used RIPA powers in specific circumstances.

The Interception of Communications Commissioner revealed in February 2015 that police forces around the country had used RIPA to access the call records of 82 journalists over the previous three years in order to identify their sources.

The Commissioner has never revealed which forces, or journalists, were involved.

Successive attempts by Press Gazette to find out more information about police surveillance of journalists using the Freedom of Information Act have been rebuffed by police forces around the UK.